A state government study surveyed a representative sample of child-care centers about childhood illnesses. Which statement BEST explains what makes the sample representative? A
Every child-care center in the state participated in the study.

B
Every child-care center in the state had an equal chance of participating in the study.

C
Every child-care center was asked a series of randomly selected questions.

D
Every child-care center that participated must have reported childhood illnesses to the state.